The p6opaque Responder Interface is the default responder for all Perl 6 objects, according to the SMOP OO API.

p6opaque Structure

class p6opaque {

has $.instanceof; # direct delegation of a single prototype, used by most object instances.
has $.WHENCE; # autovivication closure, used by autovivification
has p6opaque_proto %.proto_storage;
has Hash of Hash %.instance_storage;

}

class p6opaque_proto {

has $.how; # the metaclass instance in use
has $.who; # the package implementing this prototype
has @.isa; # an array of other protoypes
has @.does; # an array of other prototypes
has %.storage; # prototype storage (class variables)
has %.attributes; # attribute definitions
has %.methods; # methods by name
has %.submethods; # submethods by name